This invention relates to a semiconductor module having semiconductor chips packaged therein, and more particularly, to a semiconductor module which is suitable for cooling the semiconductor chip in the module.
In order to cool the semiconductor chip mounted on a substrate of the semiconductor module, it is important that the chip is thermally brought into contact with a cooling jacket, preferably, it is desirable that the chip is directly brought into contact with the cooling jacket. However, there is dispersion of height of the chips mounted on the substrate resulting from a wraping of the substrate, dispersion in size of the connecting portions between the chips and the substrate and the like. This makes it hard to bring the chip directly into contact cooling jacket.
An example of a method for making the cooling jacket come into contact with the chips uniformly includes the one disclosed in U.S. Pat. No. 4,561,011. According to this conventional technique, a heat conductive bonding agent is placed between the chips and heat conduction members disposed thereabove (FIG. 1) and the cooling jacket is pressed against the heat conduction members when the bonding agent is being solidified in such a manner that the cooling jacket and the heat conduction members are brought into close contact with each other.
However, when the above conventional method is put into practice, there arise the following problems. In a case in which an amount of supply of the bonding agent is suitable for the higher chip, the bonding agent supplied to the lower chip is allowed to spread over the entire bonding surface since the bonding surface is generally made of a material with high affinity for the bonding agent. As a result, concerning the lower chip, voids are formed in the layer of the bonding agent serving to transfer heat as shown in FIG. 2, with the result that the heat transfer efficiency is deteriorated. Further, in a case in which an amount of supply of the bonding agent is suitable for the lower chip, the bonding agent supplied to the higher chip is excessive, thereby giving rise to a problem that the excess bonding agent is poured out toward the chip connecting portion or torn into drops as shown in FIG. 3 which can cause problems, such as a short circuit. Consequently, it has been required to take measures so as to adjust the amount of supply of the bonding agent for each chip.
An object of the present invention is to provide a semiconductor module of the structure that, even if there is dispersion in height of semiconductor chips mounted on a substrate, necessary portions are filled with a bonding agent without fail while preventing the excess bonding agent from being poured out toward chip connecting portions, and a manufacturing method therefor.
Another object of the present invention is to provide a semiconductor module in which bonding agent filling portions are each filled with a sufficient amount of bonding agent so as to achieve a high heat transfer efficiency while preventing the excess bonding agent from pouring out toward the chip connecting portions to damage the same.
Still another object of the present invention is to easily manufacture a semiconductor module of high heat transfer efficiency by enabling the excess bonding agent to be held automatically in predetermined positions.
A further object of the present invention is to provide a method for manufacturing a semiconductor module which is free from a problem in which the excess bonding agent pours out toward the chip connecting portions and, hence, which can achieve a high heat transfer efficiency.